Aluminizing of cathode ray tubes



Sept. 16, 1958 w, 5, KLINDER 2,851,987

ALUMINIZING OF CATHODE RAY TUBES Filed Feb. 17, 1955 4 Sheets-Sheet 1 INVENTOR V/"//LL M707 GEOI GE @A/DE-i ATTORNEXL)" Sept. 16, 1958 w. G. KLINDER ALUMINIZING OF CATHODE RAY TUBES 4 Sheets-Sheet 2 Filed Feb. 17, 1955 INVENTOR MILL/7m GEb C-E. lF/doz ATTORNEXL'? ALUMINIZING OF CATHODE RAY TUBES William George Klinder, Pompton Plains, N. .L, assignor to Thomas Electronics, Inc., Passaic, N. 3., a corporation of New Jersey Application February 17, 1955, Serial No. 488,796

10 Claims. (Cl. 11849) television tubes, has heretofore been carried on either by means of apparatus which involved laboratory type procedure and consequently was slow and uneconomical, or by means of highly complex apparatus which carried out a multiplicity of operations in an automatic fashion.

United States Patent C) While the latter resulted in the production of coated tubes at a relatively low cost per tube, the initial investment for the coating machine was very high and maintenance costs were excessive.

According to the present invention there is provided a relatively simple machine for simultaneously applying aluminum coatings to the interior surfaces of a plurality of cathode ray tubes through the use of a single vacuum pump arrangement wherein no valves or moving parts are utilized in the high vacuum side of the system. The pumping system utilizes a diffusion pump which is heated by gas to facilitate rapid cycling. The apparatus is completely automatic and has a short pump down speed, that is, the speed with which the necessary vacuum is obtained, and has a high cycling speed. Rigid filament clamps are provided in a manner which has been found -to result in longer filament life.

It is accordingly an object of the present invention to provide a high vacuum coating apparatus which is simple in design and capable of high speed low cost operation.

It is another object of the present invention to provide "a cathode ray tube aluminizing apparatus for simultaneously aluminizing a plurality of tubes with a single vacuum system. I

It is another object of the present invention to provide an apparatus for aluminizing cathode ray tubes wherein p the high vacuum side of the apparatus has no valves or moving parts therein.

It is another object of the present invention to provide a cathode ray tube aluminizing apparatus which is completely automatic and has a high cycle speed.

. It is another object of. the present invention to provide an aluminizing apparatus for hollow bulbs which utilizes a minimum of floor space.

It is another object of the present invention to provide "an aluminizing apparatus for hollow bulbs which is simple 7 It is another object of the present invention to provide 2,851,987 Patented Sept. 16, 1958 an apparatus for aluminizing hollow bulbs utilizing a gas heated diffusion pump capable of quick heating and cooling reaction for rapid cycling.

Further objects and advantages of the invention will become apparent upon reference to the following specification and claims and appended drawings wherein:

Figure l is a side elevation of a coating apparatus constructed according to this invention;

Figure 2 is a plan view partly in section of the coating apparatus of Figure 1;

Figure 3 is a vertical sectional View of the pump 'portion of the apparatus shown in Figure 1;

Figure 4 is a detail elevation of the filament supportsv according to one embodiment of the invention; and

Figure 5 is a circuit diagram of the switches and solenoids for automatically operating the apparatus'of Figure 1. I

Referring more particularly to the figures of the drawing, there is seen in Figures 1 and 3 an aluminizing apparatus which consists of a barrel 10 containinga "diffusion pump 12 and having secured therearound an upper cooling coil 14 having an inlet 16 and outlet 18.. In the embodiment shown the diffusion pump 12 consists. of a vertical arrangement of three stages 20, 22 and 24- in which downward annular jets are employed to pump out gases by successive stages to the outlet port 26 whence they are drawn through a conduit 28 by the fore pump or backing pump, not shown. The upper cooling coil 14 has a portion Stl which encircles the outlet conduit 28 in order to prevent escape of fluid from the diffusion pump.

The boiler 32 of the diffusion pump 12 contains a conventional supply of fluid 34 such as oil which, according to the invention, is heated by means of a gas burner 36 which receives its supply of gas through a venturi 38, valve 40, pressure regulator 42, solenoid valve 44 and main valve 46. Pilot burner 48 is provided and is supplied with gas by means of a valve 50 which is connected to the main'valve 46. An internal thermocouple 52 is provided within the boiler 32 submerged in the fluid or oil 34 and having leads 54 which emerge from the top of the difiusion pump, actuate a temperature'meter 56 and thence control the solenoid valve 44. A manual switch 58 is provided in the control lines for the solenoid valve 44 and a source of electrical power, not shown, is connected to the terminals 61 for actuating this valve.

While the difiusion pump will operate with the cooling coil 14 alone, it has been found desirable to provide-a second cooling coil 62 around the lower portion of the barrel 10. The cooling coil 62 is operated independently of the main coil and is provided with an additional ther mocouple for regulating its outlet water temperature to approximately F. This serves to reduce surging and back streaming in the first stage of the diffusion pump. The gas heatwith its internal thermocouple con} trol permits a rapid change in heating rates and makes possible the almost instantaneous heat rate changes which have been found necessary for a valveless rapid cycling system.

The outlet conduit 28 is connected through pipe 64 to a valve 66 actuated by a solenoid 68 and thence through a pipeih to the backing pump, which may be of the conventional mechanical type indicated diagrammatically at 71. Between the pipes 28 and 64 there is provided a fitting 72 to which is attached an air stripping line '74 having a rubber diaphragm valve 76 therein and connected to the air stripping port of a suitable pump such as a Kinney pump 78. The air stripping line is on the diffusion pump side of the valve 66 and assists in maintaining dry oil in the backing pump and also provides negative pressure in the manifold when the first tube being coated has been removed, reducing the possibility of oil vapor or spray contamination.

The barrel 10 is provided at its upper end with a flange 8.0 to which is attachedaamanifold 82 opening into said barrel and having a pluralityof apertures ,84 therein. The apertures 84 engage exhaust conduits 86-which are in turn .connected to tube heads 88 arrangedaround :the circumference of the diffusion pump and barrel 10. Within the manifold .82 and aligned with the apertures .84..and .upper ends of exhaust conduits 86 are a plurality of hoods 89 upon which :are mounted cooling coils 98 which arein series with theupper coil 14. These coils and hoods cooperate to condense vapor from the diffusion pumpsoias to prevent any vapor .going down the ex haust tubes 86 to contaminate .thebulbs or .tubesplaced on thetube heads 88.

Each exhausttube86 has connected to its lower portion an airtube 91, which tubes areconnected to a manual --valve 92 on the manifold 82 and thence to a solenoid operated valve 94 and filter and bubbler, not shown. .When the valve 9.21s open, as it normally is inoperation, and'the. solenoid actuated valve 94 is opened during the cycle, air is admitted to the heads 88. to fill the bulbs mounted thereon and this is visually noted by the operator through observation of the bubbler.

Each tube head 88 comprises a cylindrical body 96 having a top flange 98 and bottom 1.01. The top flange 98 -is provided with a rubber sealing washer 100 for providing an hermetic sealbetween a.bulb,102, shown in dotted .lines, and the head 88. Mounted on the bottom 101 ofthe body 96 is a filament holder indicated generallyat 104. The filament holder preferably consists of a pair of elongated rods 106 and 108 which are mounted in the bottom ltll of the body 96 and are connected .by means-of the cable .110 to the switch. box 112 on top of the manifold 82, and thence to asupply of filament power, not shown in Figure l. The upper portions of the filament holder rods 1.06 .and 108 have mounted thereon rigid bars .114 having an outstanding stud 116 and a .pincer arm 118 pivoted thereto and urged into engagement therewith as by means of a spring 120. The arms 114are afirxed to tubes 121, as by brazing .or welding, and the tubes .120 .are provided with threaded studs .122 and 124 for receiving. set screws 126. to lock the pincer assemblies to the rods 106 and. 10,8. .Further bracing of the .pincer assemblies is provided by means of an insulating plate 128 which is screwed tothe lowermost portions of the farms 114 by means of bolts 129 engaging threaded apertures 130. The. resulting filament holding assembly is extremely sturdy and rigid and has been found to result in ,appreciably lengthened filament life.

According to the preferred embodiment of the invention the pincer elements of the electrode holders clamp the opposite ends of a coil 132 of a refractory metal wire such as tungsten, molybdenum, or similar metal. The aluminum is then inserted into the turns of the coil 132 as a thin strip which may be corrugated so that each corrugation engages a turn of the coil. As an alternative the coil 132 mayitself be formed of aluminum and be replaced at .the end of each cycle of operation.

.Each tube'head assembly 88 is supported by means of a bracket 134 and bolt assemblies 136 and 138 upon any suitable support structure.

Referring to Figure there is shown a schematic diagram of the circuit of the automatic controller for the coating apparatus of this invention. A cam switch assembly indicated generally at 140 is provided with a cam actuating motor 142 connected to power leads 144 and 146 through .a starting button 148. 'The motor 142 is shunted by a clutch coil 150 which actuates'a'set of contacts 152 for locking the circuit on after the starting button 148 has been released. A start-cycle pilot light 168 is placed across the leads 144 and 148 to indicate that the motor is energized. The motor 142 drives a cam shaft, not shown, which actuates a series of switches 154, 156, 158, 160, 162 and 164. One terminal of each of these switches is connected to the supply'line 146 while the other terminals are connected in the following manner.

Normally closed switch 154 is connected to the winding ing 166 of the air inlet solenoid actuated valve 94 and this winding is connected to a connection 170 which leads to the supply line 144. The :switch 156 is connected to a winding 172 on the solenoid actuated valve 68 and to a winding 173 on the gas supply valve 144. The other sides of these windings are connected to .the'line 170. The temperature control meter 56 is placed in series with the winding .173 for the gas supply valve. .Theswitch 158 is connected to a winding 174 on a relay having normally colsed contacts 176. The contacts 176 are in turn connected to a portion 178 of a transformer winding 180 and to a lead 181 connected to the supply lead 146. The other lead from the :portion 178 of the transformer winding 18.0 is connected to the line 17.0. .The switch 160 is similarly connected to a winding 182 of a relay having normally closed contacts 184 and these in turn are connected to lead 181 .and to a second portion 186 of the transformer winding 180. The switch ,162 is also connected to a winding 188 of a relay having normally closed contacts 190 which are connected toa .final portion 192 of the transformer winding 180 and to the line 181.

The. transformer winding'180 is provided with asecond- .ary .193 which is connected to the filaments .132. The final switch 164 isconnected to a light cycle off .bu1b5194.

.Theoperation of the coating apparatusis v.asfollows; the .difiusion pump 12, backing pump, and air stripping pump 78 are started and thin strips of aluminumare placed in the coils of the refractory filaments .132. .Bulbs or tubes to be coatedare then mounted in snug relationshipwith the washers and the machine is .readyfor cycling.

U -pondepressing .thestarting button 148 the .motor 142 is energized and .the clutch coil .150 causes the switch 15.2.10 close to hold the motor in an energized condition after the starting button is released. Light 168 is also energized at this stage. When the motor starts torotate the cam shaft causes, switch .154 to open de-energizingthe coil 166 of .the .air inlet valve .94. This .closes theair inlet .valve 94 thereby preventing air from .enteriugthe exhaust conduits 86 through the tubes 90. The .cam shaft'then causes closure .of switch 156 which energizes the coil 1.72 of the-solenoid actuated valve 66, opening the valve between the diffusion pump outlet conduit 28 and the conduit 70 to the backing pump, and also switching on gas heating via the solenoid winding 173 for gas supply valve 44. This causes a rapid creation of a high vacuum in the tube heads 88.

At the start of the rotation of the cam shaft, :the switches 158, and 162 are all maintained in .a closed position thereby opening the contacts 176, 184 and 190 so as to remove voltage from the transformer winding and thus from the filaments 132. After the .cam shaft 'has advanced far enough to cause the switch 156 to close, thereby opening the solenoid actuated valve 66, the cam shaft next causes switch 162 to open thereby de-energizing relay winding 188 and permitting-contacts to close. This provides a line voltageto the entire Winding 180 including portions 178, .186 and 192 and produces a low voltage in the secondary 193, as for example, a voltage of approximately two volts to provide for degasingof-the aluminum strip and filament.

The cam shaft then advances further to open switch 160 'andsimultaneously close switch 162 to thereby de energize relay winding 182 to permit contacts 184 to close, while energizing relay winding 188 to open contacts 190. This provides voltage to portions 178-and 186 of the transformer winding 180 thereby increasing the secondary'to primary turns ratio and increasing'the voltage in the secondary 193 to a higher value, asior amp-e;

instance, to approximately five volts. This increase in the heat of the filaments 132 causes vaporization of the aluminum strip.

Further movement of the cam shaft next causes an opening of switch 158 and a simultaneous closing of switch 160 to de-energize relay winding 174 and energize relay winding 182, This permits contacts 176 to close while contacts 184 open, thereby applying voltage to portion 178 of the transformer winding 180. The secondary to primary turns ratio is thus further increased so as to provide a secondary voltage in the winding 193 of, for instance, approximately seven volts which is utilized to insure that no aluminum is left in the filament.

Subsequent rotation of the cam shaft causes. switch 158 to re-close thereby opening contacts 176 and also causes switch 164 to close to light the cycle-off lamp 194 and finally to open contact 156 and close contact 154, to thereby complete a coating cycle.

It will be apparent from the foregoing that a coating apparatus has been provided utilizing simple compactly arranged parts wherein a single pumping installation is utilized having no moving parts or valves in the high vacuum side of the system. Rapid control of the heat for the diffusion pump permits a rapid cycling without the necessity of high vacuum valves and the hooded cooled high vacuum conduits prevent the contamination of the tubes by the diffusion pump fiuid without the necessity for valves being interposed in the system. Rigid filament mountings are provided at the .tube mountingstation and these greatly extendthe normal life of the refractory metal filaments used. The resulting device is low in installation cost, low in maintenance cost, and capable of cycling automatically with great rapidity to produce aluminum coated cathode ray tubes with brighter aluminum coatings.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. An apparatus for coating the interior surfaces of tubes with metal comprising in combiantion; mounting means for holding a plurality of said tubes in hermetic connection with a plurality of conduits, a container having a manifold at the top thereof opening thereinto, a

dififusion pump in said container, said conduits being.

connected to said manifold to continuously maintain communication between said mounting means and container, an outlet connection near the lower end of said container, said diffusion pump having a backing pump associated therewith, a conduit connected to said outlet and to said backing pump, a valve in said last named conduit, a stripping conduit connected to said last named conduit on the container side of said valve, a vacuum pump connected to the other end of said stripping conduit to draw air through said conduits and container when at least one of said conduits is not in hermetic connection with a tube, and cooling means on said container.

2. An apparatus for coating the interior surfaces of tubes with metal comprising in combination; mounting means for holding a plurality of said tubes in hermetic connection with a plurality of conduits, a container having a manifold at the top thereof opening thereinto, a diflusion pump in said container, gas heating means for said diffusion pump, said conduits being connected to said manifold to continuously maintain communication between said mounting means and container, an

6 outlet connection near the lower end of said container, said diffusion pump having a backing pump associated therewith, a conduit connected to said outlet andto said backing pump, a valve in said last named conduit, a stripping conduit connected to said last named conduit on the container side of said valve, a vacuum pump connected to the other end of said stripping conduit to draw air through said conduits and container when at least one of said conduits is not in hermetic connection with a tube, a first cooling means on said container, and a second cooling means on the lower portion of said container. 7

3. An apparatus for coating the interior surfaces of tubes with metal comprising in combination; mounting meansfor holding a plurality of said tubes in hermetic connection with a plurality of conduits, a container having a manifold at the top thereof opening thereinto, a diffusion pump including a fluid containing boiler in said container, gas heating means for said diffusion pump including an electrically operated gas supply valve, said conduits being connected to said manifold to continuously maintain communication between said mounting means and container, said diifusion pump having a backing pump associated therewith, an outlet connection near the lower end of said container, a conduit connected to said outlet and to said backing pump, a valve in said last named conduit, a stripping conduit connected to said last named conduit on the container side of said valve, a vacuum pump connected to the other end of. said stripping conduit to draw air through said conduits and container when at least one of said conduits is notin hermetic connection with a tube, a first cooling means on said container including aportio'n encircling said outlet connection, a second cooling means on the lower portion of said container, and a thermocouple in said fluid in said boiler connected to control said gas supply valve.

4. An apparatus for coating the interior surfaces of tubes with metal comprising in combination; means for holding a plurality of said tubes in hermetic connection with a plurality of conduits, a container having a manifold at the top thereof opening thereinto, a diffusion pump in said container, said conduits being connected to said manifold, a downwardly directed hood mounted in said manifold at each conduit connection so that gases passing through said conduits must pass through said hoods, cooling means for said hoods, said diffusion pump having a backing pump associated therewith, an outlet connection near the lower end of said container, a conduit connected to said outlet and to said backing pump, a valve in said last named conduit, a stripping conduit connected to said last named conduit on the container side of said valve, a vacuum pump connected to the other end of said stripping conduit, and cooling means on said container.

5. An apparatus for coating the interior surfaces of tubes with metal comprising in combination; means for holding a plurality of said tubes in hermetic connection with a plurality of conduits, a container having a manifold at the top thereof opening thereinto, a diffusion pump including a fluid containing boiler in said container, gas heating means for said diffusion pump including an electrically operated gas supply valve, said conduits being connected to said manifold, a downwardly directed hood mounted in said manifold at each conduit connection so that gases passing through said conduits must pass through said hoods, cooling means for said 'hoods, said diffusion pump having a backing pump associated therewith, an outlet connection near the lower end of said container, a conduit connected to said outlet and to said backing pump, a valve in said last named conduit, a first cooling means on said container, including a portion encircling said outlet connection, a second cooling means on the lower portion of said container, and a .ihermocouplein said fluid in said 'boiler connected to control-saidgas-supply valve.

' 56. A 'fast :cycling a paratus for coatin :the=inter ior surfaces of tubes :with metal comprising in-com-bination; mounting means for holding a plurality of said .tubes' in hermetic connection with -a plurality of eon'duits, a diffnsion pump-eontinuously connected tosaid conduits and mounting means, saidditfusiodpump including a-backing pump-connected to the'discharge thereof, and-a stripping pump connected to said discharge ofsai'd difiusion pump to draw air through said :conduits difiusion pump 'when at least one of said conduits is not in hermetic connection-witha tube. V

'7. A fast cycling apparatus for coating :the interior surfaces of tubes with metal comprising incombination; mounting means 'for' holding a plurality of .said :tubes in hermetic connection witha-plurality of conduits, :a "first valve connected 'to said conduits-and to the atmosphere, a--'difiusionpump continuously connected to saidieondnits and mounting means, said .difiusion including a backing pump connected to the-discharge:thereofithrough a second valve, "heating means for saidldifiusion pump, and a stripping pump connectedutosaid Sdischar-geof said diffusion pump on'thedifiusion pump side of said second valve to draw air "through said-conduits and diffusion pump when at Jeastone of said :con'duits is'wnot in hermeticconnection With=a.tu'be.

*8. apparatus as setout in-iclaim 7 including..:control means for performing in sequence the --fo1lowing operationseach time a tube is coated, closing sa idfirst valve, "opening said second valve energizing said heating means and drawing air throughsaid'diifusion pump why meansofsaid str ippingpump.

9. Ail-apparatus for coating the interior surfaces "of tubes :with metal'comprisingin combination, a vertically mounted container having a manifold atvthe top thereof opening thereinto, :a diffusion pump in said container, a: plurality of vertical tube mounting cylinders stationarily mounted about -;said container, :conduits connected to said cylinders and-entering said manifold substantially radially, aa downwardly directed hood mounted in said manifold :at eachrconduit connection so that gases passingzthnough said conduits must pass throughsaid hoods, andrcnoling means ion said hoods.

l0. Anappanatus as :set out in claim -9 wherein said diffusion :pump has ':a:hacking pump associated therewith through a discharge conduit on said container, and a stripping-pump :connected to said dischargeconduit.

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